Principals say that good state grades portend a bad report the next year because room for improvement is small and avenues to failure are many.

Safety Harbor Middle School principal Sally Barker knew as soon as she saw the Florida Comprehensive Assessment Test scores that her school would likely lose its A.

Test scores showed the number of low-performing readers had increased from 7 to 12 percent.

"Guys, we're about a hair away from a C," Barker told teachers.

When the state issued its grades last week, Safety Harbor tumbled to a C. The state places a great deal of emphasis on reading, long considered the gateway subject. Schools wanting to retain their grades must see more of their students reading at a higher level than the previous year. If not, they succumb to what Barker calls a "narrow margin of error."

For that reason, principals and teachers realize they don't have any room to boast about grades.

"Once at the top, it's hard to stay at the top," said Cindy Burns, a sixth-grade language arts teacher at Safety Harbor.

Others agree.

Just 15 minutes after administrators at Largo Middle School learned the school received an A, principal Bill Cooper started worrying about whether the school could retain the grade next year.

"It's fragile," Cooper said. "A small percentage of children can make or break you."

It is almost impossible to stay on top. Of the more than 100 schools tested in Pinellas during the past three years, only three have received straight A's.

Coachman Fundamental Middle School received two A's before receiving a C this year for posting increases in low-performing readers.

Principal Dawn Coffin wishes Coachman had not done so well in the first two rounds.

"There comes a point where you have nowhere to go but back. You can only maintain it for so long. It's better to be at the bottom and move up," she said.

The state further complicates matters from year to year by changing factors that contribute to a school's grade. Last year, for example, the test scores of students who were considered "mobile" were not counted in the grades, and more than 100 schools statewide watched their scores rise. In another change this year, the scoring for questions requiring short and long answers -- the most difficult questions -- was not completed in time and, thus, not counted in the school grades.

"Who knows what they're going to judge it on?" said Pat Huffman, principal at Belcher Elementary, which skyrocketed from a C to an A.

And each year a different group of students, with different academic strengths and weaknesses, is tested. For example, 25 of the 180 fifth-graders have been identified as gifted at Bauder Elementary School in Seminole and set a standard against which next year's students will be measured. The upcoming fifth-grade class has 150 students. Only seven are gifted, principal Jan Johnston said.

"You've got to rise higher than that. You've got to beat that standard. That's hard when you're talking about different kids."

As a school moves more students into high-performing levels, it is more difficult to maintain a high grade.

Dunedin Highland Middle School, for example, saw a decrease in the number of students reading at the lowest level from 23 percent to 17 percent. The school needs to get that down to 15 percent next year to try to hang on to its A, principal Peggy Landers said.

"What happens if we only go to 16? Does that mean we're not a good school?"

Principals say the answer to that question is no.

They don't think a school can change so drastically in only one year.

But they do think they can learn from the testing experience.

"I think our kids really tried," Coachman's Coffin said. "But I don't think we did enough practice with the reading as well as we did with the math."

Long before students were tested, Safety Harbor teachers had planned to target reading next year, Barker said.

Coming this fall: Read 180, a program that uses computer software combined with independent reading and one-on-one attention to help boost reading skills.